Some computer programs were developed to analyze the earthquake responses of horizontally irregular grounds and their corresponding earthquake damage mechanism using the "Pseudo-Spectral Method." These programs include several new methods: it can analyze seismic responses separately for SH wave and P-SV waves; it can effectively absorb artificially-generated waves at the analytical boundaries; and it can capture clearly the process in which the short-period surface waves are secondarily generated due to horizontally irregular grounds. In addition, we developed a new technique by which the generation processes of short-period surface waves can be visually and dynamically expressed on the display of computers. This technique enables us to interpret detailed propagation mechanism of short-period surface waves. We also analyzed array strong-motion records to estimate strains and stresses related with short-period surface waves. This analysis made it clear that short-period surface waves produce large strains leading to earthquake damage of various kinds of structures such as buried life-line structures. Finally we published a report to compile the above outcomes derived by this research project.アレー観測システムKASSEMの強震記録を用いて地盤に発生するひずみと短周期表面波との関係を明らかにした.その結果,ひずみは加速度記録の主要動に関係なく後続の加速度の小さい相でむしろ大きくなること,これらのひずみの実測記録を含めてKASSEMの実測加速度記録と同システムの展開されている不整形地盤を対象にした応答シミュレーション結果を比較した結果,両者は波形,振幅,継続時間でよく一致すること,その応答挙動は単周期表面波によって強く支配されることが明らかにされた.